STE. GENEVIEVE MARLS NEAR FORT DODGE 613 



Occurrence. — Ste. Genevieve, Pella beds, along' Lizard creek 

 and in the Illinois Central railroad cutting, Webster county, 

 Iowa. 



G-irtyella indianensis (Girty) 



Plate XII, figs. 12-13. 



1914. Girtyella indianensis Weller, Geol. Surv. 111., Monog. I, 



p. 275, pi. XXXIV, figs. 1-24. 



Shell small, smooth, elongate, more or less oval to roundly five- 

 sided in outline; front margin truncate. Dimensions of the most 

 perfect specimen found at this locality are: length 15 mm., width 

 10.5 mm., thickness 7 mm. 



Pedicle valve convex, greatest convexity over the uuibonal re- 

 gion, mesial sinus shallow and limited to the anterior third of 

 the valve ; beak prominent and strongly incurved over that of the 

 brachial valve and terminating in an elongate ovate foramen 

 which opens through the terminal part of the umbo. 



Brachial valve less convex than the pedicle, mesial fold ill-de- 

 fined or wanting, beak curved beneath that of the pedicle. 



Surface of both valves smooth except for a few concentric lines 

 of growth. Veiy fine punctae which are characteristic of this 

 genus may be readily seen with a lens. 



This species is very rare in the Pella beds at Fort Dodge though 

 abundant in corresponding beds in southeastern Iowa. Only 

 two specimens have been obtained. By several geologists this 

 shell has been called Dielasma turgida but it has been shown by 

 Girty to differ from that species. From the young specimens of 

 Composita trinuclea the young shells of this species may be dis- 

 tinguished by the shape of the foramen and by the fact that the 

 shell structure of G. indianensis is always punctate. 



Occurrence. — Ste. Genevieve, Pella beds, along Lizard creek, 

 Webster county, Iowa. 



Spirifer pellaensis Weller. 



Plate XII, figs. 23, 28-34. 



1858. Spirifer keokuk var. Hall, Geol. Iowa, vol. I, pt. II, p. 677, 



pi. 24, figs. 4a-d. 

 1914. Spirifer pellaensis Weller, Geol. Surv. 111., Monog. I, p. 340, 

 pi. XLV, figs. 1-31. 

 Shell of medium size, in most cases wider than long, greatest 

 width at the hinge-line but in a few cases in front of the hinge- 

 line, cardinal angles extended, rectangular, or in a few cases 



